The present invention relates to a system added onto and assembled with a conventional camera. The system increases the horizontal field of view of the camera and decreases the vertical field of view of the camera. The system is characterized by at least two pairs of plane mirrors.
Standard optical instruments, cameras and terrestrial viewing systems, such as telescopes and binoculars are typically configured to have the same horizontal and vertical fields of view because optical instruments are typically constructed with spherical optics.
In terrestrial surveillance systems, a larger horizontal field view is preferred, so that more of the horizon may be imaged without having to adjust, e.g. rotate, the instrument around a vertical axis.
Thus there is a need for and it would be very advantageous to have a simple optical system which may be added onto a standard camera, which increases the horizontal field of view of the camera at the expense of the vertical field of view without requiring an internal modification of the camera.
Prior art solutions for increasing the field of view of a camera include, using more than one camera A representative prior art reference which discloses use of more than one camera for increasing the field of view is U.S. Pat. No. 5,532,737. Another prior art method for increasing the field of view of a camera, without modifying the camera uses external curved mirrors. A representative prior art reference which discloses an external convex mirror for increasing the field of view is U.S. Pat. No. 5,790,181.
U.S. Pat. No. 4,288,819 discloses a multi-field imaging device for directing light from a first optical field and a separated second optical field into a video camera used for security surveillance thereby reproducing a split-screen image with the video camera. The multi-field imaging device can be aligned whereby light from the second optical field is directed directly onto one side of an image plane. A pair of mirrors are adjusted so that light from the first optical field is reflected by the mirrors to the image plane in a juxtaposed relation with the light from the second optical field. The image plane is positioned at a predetermined distance from a lens of the video camera whereby images directed on the image plane are reproduced by the video camera